The interfacial properties of perfluoropolyether (PFPE) films having the [(CF₂)_nO] main chain with n = 1.5, 3 and 4, were systematically compared on carbon surfaces. The monolayer thickness decreases with increasing n, indicating that stiffer chains (larger n) lie flatter on the surface. The surface energy-derived disjoining pressure also increased with increasing n. Spin-stand tribological experiments indicated that clearance (slider-disk spacing) increased and PFPE lubricant pick-up decreased with increasing disjoining pressure and main chain stiffness. Slider wear rate increased with decreasing PFPE coverage and increasing main chain stiffness. Structure-property correlations are developed and discussed.